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<br />Permanent Pond Spillways <br />The sediment pond will maintain the current 4" steel pipe in the dam to act as the <br />primary spillway to dewater large volumes of water in the pond. This spillway is <br />located only 1.5 feet from the pond bottom. It has been in place for many years without <br />a problem. <br />A new emergency spillway is proposed for the permanent pond embankment, although <br />the pond will hold the entire flow from the 100 year 24 hour event. This design is <br />based on a trapezoidal spillway with riprap lining to handle a flow of 2.26 cfs with 1.0 <br />feet of freeboard. <br />The Sedcad 4.0 storm mparameters are shown below: <br />Generallnformation <br />Storm Information: <br />Storm Type: NRGS Type II <br />Design Storm: 25 yr - 24 hr <br />Ralrfall Depth: 2.W0 Indies <br />The watershed is based on a drainage area of 3.5 acres of average curve number of 80, <br />which accounts for reclaimed area of approximately curve number 74 and some road <br />areas and road cuts of curve number 86. This results in a peak discharge of 2.26 cfs <br />and a runoff volume of 0.164 ac-ft, as shown below: <br />subwatarshed Hydrology Detail: <br />Stn SV/5 SK5 Area lime ~ Musk K Curve Fmk Runoff <br /> Con[ MuskX UN5 Di5thargE Volume <br /># # (acj this) (hr5) Number (~) (ac_ft) <br />#1 1 3.500 O.OOD O.D00 0.000 80.OOD M 2.26 0.169 <br /> 3,500 2.26 0.164 <br />183- l <br />i7~l3 <br />